High-flying career and a fulfilling personal life? It can't be done, says Elizabeth Perle McKenna, and women shouldn't even be trying. We gave her new book to 20-something Clare Garner and, opposite, working mother Diane Coyle. Here is their response.

A new generation of young women takes for granted that they can succeed in a man's world, on men's terms, and weather with ease all the attendant pressure, politics and stress. There may be a price to pay in their personal lives, but it's worth paying in the brave, new, downsized world.

However, according to an older and therefore wiser American woman, who woke up and smelt the coffee at 40, it doesn't have to be this way. What's more, there is trouble ahead for any woman who builds her identity solely around her work. After the women's movement, she says, comes a second battle: the battle for work to take its due place along all the other important aspects of our lives.

Elizabeth Perle McKenna, a former publishing executive, describes her book When Work Doesn't Work Anymore, published here this week, as a "wake- up call" to all women who feel there is an increasingly adversarial relationship between the professional and and the personal. We've got the solutions, she says. We just don't dare implement them.

She argues that women are imprisoned by the very thing they thought would set them free. They may have parity, but it's making them miserable. The solution, she says, is to fight for a feminised workplace. But this battle is harder to win than the original one for equality. "The women's movement was founded on anger," she explains. " It is very hard to do this second movement because it is founded on depression."

To any 20-something woman who is lucky enough to have landed a job in her chosen career all this may come as a bit of a shock. Success equals a good job and who they are is, to a large extent, defined by what they do. But are they being honest? On the surface, work gives self-esteem and financial independence, but, secretly, some women are already feeling a bit jaundiced. They know that these days a job is not for life and that no amount of sacrifices will guarantee promotion or, more important, deep personal happiness. They want to work, but not at the expense of everything else.

Take one friend of mine, Mary, a 30-year-old marketing executive. On hearing about Miss McKenna's book she said wistfully: "Is she saying we should give up? I think we should." Hang on a minute. This from a woman who is about to take up the offer of a bigger and better job, complete with company BMW. Surely some mistake?

"It's five days to two days," she explained. "That's the wrong balance. You spend the majority of your life working and, even if it's enjoyable, it's stressful. I could take a four-day week in my present firm, but pride stops me. It's convention that's forcing me on to make that next step." She is, according to McKenna, a prime example of the legions of women who are "outwardly successful and inwardly wanting".

But what should they do? Are they on course for a full-scale collapse at 40? Downshifting before 30 - before they've even started a family - sounds absurd. McKenna would say that if they are to avoid feeling washed up, bitter and betrayed 10 years down the line, eating too much, drinking too much, weighed down with exhaustion and depression, they must, apparently, heed her story.

She should know. For 20 years she followed a one-track path. Her career ("as good as my father's") was "sacred ground and synonymous with who I was". Working met her "financial, emotional, intellectual and self-esteem needs".

"Through my twenties I concentrated on work. I worked at work, flirted at work. Occasionally, I dated at work. I loved work and felt a puffed- up pride at having to spend a Saturday at the office; it made me important." Her account may sound a bit extreme, but she is the product of American corporate culture which is probably more demanding and work-obsessed than the British equivalent. Nevertheless, we all know people whose work is their life and they are proud of the fact.

In her early thirties, McKenna's road began to narrow. Her self-esteem was "in the toilet from trying to be everything to everyone and ending up being nothing to myself". She had "indigestion in my soul" and was experiencing "a subtle but consistent atrophying" of the importance of other aspects of her life. By her late thirties, she had a son and her life was becoming increasingly unsatisfactory. She found herself faced with an all-or-nothing choice between "meaningful work" or "some 1950s home fantasy". She resented the choice, "but there it was". When she finally decided to walk out of the office door, she immediately felt a "non-person", her whole identity collapsed and in the first week without a paycheck she became "worthless instantly". Not a pretty prospect.

Brenda Barnes, who recently resigned from her job as president and chief executive of Pepsi-Cola's North American operation to spend more time with her family, is an extreme example, but an example nevertheless of "the system that creates these idiotic choices", says Miss McKenna. Sometimes only a grave illness stops us in our tracks, sometimes the way we work can be "fatal".

Her answer is to change the present rules for success, ie Rule 1: Work comes first, above all personal or family concerns. Rule 1a: If you're a man you can break rule 1 and be a great guy; if you're a woman and you break rule 1, you're not serious about your future. Rule 2) Long hours are a requirement... She advocates four-day weeks so that we can live more balanced lives, citing research which shows that most people can cut 20 per cent of their salary and maintain their lifestyles. But she rejects the term "downshifting", implying as it does a diminution and suggests that we must learn not to put "all our eggs in one briefcase".

She points out, quite rightly, that one of the most potent barriers to leaving a career path, even for a year or two, is the fear of not being able to return. Women fear they will end up taking what Miss McKenna calls "Mommy Track" jobs - repetitive, lower-status work - which in turn cause stress.

So how convincing is she? A porous work environment in which we could come and go, be enriched, rich and fulfilled at any one time sounds wonderful. But, sadly to me and most of my contemporaries, the idea of putting up our hands and demanding a four-day week or refusing to work long hours would be tantamount to career suicide. If we decide to take a few years out, can we seriously expect to hop back on the same rung of the ladder?

I wish your were right, Miss McKenna, but I fear you may be leading us down the Mommy Track before we are even Mommies.

'When Work Doesn't Work Anymore' by Elizabeth Perle McKenna is published by Simon & Schuster this week, pounds 14.99.

Young women are being sold a pup by Elizabeth Perle McKenna and similar backlash authors, writes Diane Coyle. And it is such a seductive argument to put to people who are working incredibly hard compared to 20-somethings a decade ago, when I was in the early stages of my career.

It goes as follows: you are an ambitious professional woman who wants to get to the top in your chosen career. You will accomplish this but at the expense of your personal life and, especially, having a family. In a decade's time, when your biological clock is winding down, you'll regret your choices. Escape from this unfair dilemma by opting out of the rat race on your own terms now!

Enough of this is true to make it seem a valid argument. A lot of professional jobs make unacceptable demands on family life (for both women and men). A lot of 30-somethings (both female and male) are stressed and unhappy. Men are expected to do it all, too, these days, work 10 hours and then go home and change nappies.

It is true to say that the demands of work have increased. Career-track jobs not only demand long hours in the office, they follow their victims everywhere, all the time, thanks to pagers and mobile phones.

The logic fails, though, in claiming that there are only two choices, and that only women have to make them. The world of work is imperfect, but it is not an either/or place. You do not have to either be a brilliant success in your career or stay at home with the kids, your self-esteem draining away. And because the world is a subtler place than that, there is no need to demand utopian change in the workplace.

Now, I'm no Nicola Horlick, running my large household like a small business and doing a high-powered City job on the side. But I do have a demanding job that I love and a husband and son whom I also love. When my son was a baby, I dropped off the career track for three years to work from home. Then I scrambled back on.

This is nothing special. Lots and lots of mothers work. We "career women" have to make sacrifices. You miss some of those incredibly rewarding moments in a child's development. You also miss some incredibly important meetings at the office. Does this mean it isn't worth trying to find a compromise in the imperfect world that we face? Absolutely not.

Obviously, this is not necessarily easy. You need luck - if you have children who are sick or you need to sleep 12 hours a night, it will become much harder. You need to be prepared to put up with imperfections and with being slightly shambolic in all areas of your life. You have to work hard and be organised. You have to give up things like nightclubbing, or leisurely days shopping or catching the latest movies. What I miss most of all is time to myself, because there are constant demands from both home and work.

I don't think any woman or man who works would oppose changes that made the workplace less rigid and the choices therefore less difficult. This will happen, slowly. For one thing, the public culture is changing the further behind we leave the harsh Thatcher era.

More important, there is a shortage of young people. Our population is ageing. In the latest year for which figures are available, the number of 16 to 25 year olds in Britain fell by 78,000, and the number of 25 to 30 year olds has fallen by 180,000 over three years. Before long, employers will be forced to make work more attractive to those starting out on their career.

But altering working patterns would not prove a panacea. When there are choices, there is bound to be a need for compromise. How much better to have the choice of several ways to be able to fill your time, and to have a stab at a top-flight career even if it presents you with some difficult dilemmas, than not to have the option at all.

Ms McKenna says we need to redefine success, to stop equating it with an all-absorbing, high-flying career that has been designed to suit men. She ignores the old feminist insight that it has been designed to suit men because it is success. We women should still want it. Still, I wish Ms McKenna well in her personal effort to adopt a lower profile and spend more time with her family.

Diane Coyle is economics editor of 'The Independent'